The invention relates to an apparatus for reducing a stack of flat, flexible articles by sequentially removing the articles from the underside of the stack.
A stack reducing apparatus of the described type is known from CH 598 106 and corresponding U.S. Pat. No. 4,127,262. The apparatus disclosed in these documents comprises a supporting apparatus made of spaced-apart rollers which are moved along a continuous circulatory path and can be rotated freely about their longitudinal axis. The rollers form, in a portion of the supporting apparatus, a rest in the form of a roller pathway upon which a stack of sheet-like articles rests. The rollers are moved through beneath the stack, with the stack always resting on a plurality of rollers. A cyclically driven suction element has access to the stack from beneath, through the interspaces between two rollers, and raises off in each case one corner of the currently lowermost product from the rest of the stack. At least the following roller of these two rollers, as seen in the direction of circulation of the continuously moving roller pathway, moves into the interspace between the raised-off corner and the rest of the stack and thus peels off the lowermost product from the rest of the stack. The stack is fixed laterally by supporting elements. The drawn-off product comes to rest on a belt conveyor arranged beneath the stack rest. The deposited products form an imbricated formation, which is transported away continuously.
The problem with the above described apparatus is that the space taken up by the rollers constitutes a cylinder casing or xe2x80x9cwallxe2x80x9d having a fixed cross-sectional surface area and a certain width which is at least equal to the length of the rollers. This space is thus blocked by the roller pathway or the supporting apparatus, and it is thus necessary for the belt conveyor to be arranged obliquely in relation to the circulatory path of the rollers and to route the removed articles laterally out of the region of the supporting apparatus. The overall arrangement, comprising the supporting apparatus and the belt conveyor, thus have a considerable lateral extent, which greatly exceeds the stack width. It is not possible for the stack-reducing apparatus to be realized in a compact manner. If, furthermore, the intention is to produce on the belt conveyor an imbricated formation with the edges of the products running perpendicularly and/or parallel to the removal direction, it is necessary to orient the stack on the stack rest obliquely in relation to the rollers. As a result, shortly prior to being deposited on the belt conveyor, an article is only retained at one corner. When the article is deposited, it is thus possible, in particular at high stack-reduction speeds, for this to result in twisting and thus in undesirable mechanical loading of the article and in a non-uniform imbricated formation.
An object of the invention is to develop an apparatus for reducing a stack of flat, flexible articles of the above described type such that the lateral extent of the apparatus is minimized.
It is a further object of the invention to render it possible for the articles, even at high speeds, to be transferred reliably to the belt conveyor in a defined orientation.
The above and other objects and advantages of the invention are achieved by the provision of an apparatus of the described type wherein the product stack is supported from beneath by a plurality of bearing elements, which slide through beneath the stack. The bearing elements form part of a supporting apparatus, and they are preferably fastened, at one end, on a conveying element which is moved along a continuous circulatory path. In the region of the stack rest, the bearing elements preferably run horizontally and parallel to one another. It is particularly preferable for their axes to be located in a common horizontal plane or slightly curved surface which constitutes the stack rest.
The bearing elements are preferably rollers which can be rotated freely about their longitudinal axis and roll with a low level of friction on the articles which are to be removed. The bearing elements are configured and driven, for example, as is described in CH 598 106 and U.S. Pat. No. 4,127,262.
According to the invention, the bearing elements can be pivoted or displaced such that it is possible to change their position or orientation relative to the circulatory path. The circulatory path referred to here is the circulatory path of the bearing points of the bearing elements, of which the position relative to the conveying element does not change. The circulatory plane referred to is the plane in which the circulatory path is located. If the circulatory path is a three-dimensional curve which is not located in one plane, the circulatory plane referred to is the plane by which the three-dimensional curve can be approximated locally.
The space covered by the rollers is formed, according to the invention, such that the removal arrangement can be routed out of the region of the supporting apparatus in a space-saving manner. At the location where the belt conveyor is spaced apart from the circulatory path to the smallest extent, i.e. where the belt conveyor extends through the circulatory path when viewed in side elevation, the rollers are pivoted or displaced and thus free the path for the belt conveyor. The belt conveyor may be arranged directly beneath the stack rest. The apparatus according to the invention may thus be of very compact design.
In a further preferred embodiment, the bearing elements are oriented parallel to the leading and/or trailing edge of the stack. This is because the invention renders it unnecessary for the stack to be positioned on the stack rest obliquely in relation to the bearing elements. This means that a separated-off article is always retained over its entire width until it is separated off completely. When it is deposited on the belt conveyor, it is not twisted, even at relatively high stack-reduction speeds.
The supporting arrangement may be designed in one or two parts. The single-part version has a pathway made of bearing elements fastened pivotably at one end on a conveying element. In order for the stack to be well supported, said bearing elements may be supported by a rail, at their free end, in the region of the stack rest. The separating element has access to the lowermost product, through the interspace between two bearing elements, for example as in CH 598 106 and U.S. Pat. No. 4,127,262. It is operated cyclically in adaptation to the spacing between, and the speed of, the bearing elements.
The two-part configuration has two roller pathways, of which the rollers or bearing elements are located in a common plane in the region of the stack rest. The bearing elements of the first and of the second roller pathway are each fastened on a respective first and second conveying element and can be displaced or pivoted relative thereto. The belt conveyor is preferably arranged between the conveying elements.
An example of such a two-part roller pathway is described in the application PCT/CH00/00530, which was not published before the priority date. The arrangement of, and means of controlling, the rollers of which use is made in said application may also be used for the present apparatus.